Prostaglandins (PG) are proposed to be important regulators of cellular metabolism. It has been previously demonstrated that elevated (and possibly other aberrations) in PG synthesis or metabolism as occurs in the synovium in inflammatory arthritis, has an inhibitory effect on the adjacent articular cartilage and may be responsible for the initiation and/or progression of cartilage destruction in this disease. Environmental parameters similar to those which may occur in rheumatoid arthritis are being studied in in vitro systems of cultured synovial tissue and in isolated suspended chondrocytes. The endogenous PG synthetic capacity and kinetics of PG synthesis are being examined in an isolated chondrocyte preparation. The effect of temperature on the efficacy of nonsteroidal anti-inflammatory agents is being examined by measurement of PG synthesis and metabolism of labeled intermediates of macromolecules of cartilage. Mechanisms of action of PG on both chondrocytes and rheumatoid synovial tissue will be explored by measurement of rates of m-RNA translation in a cell-free preparation and by determining the role of PG as auto-oxidized fatty acids causing the the production of degradation products which destroy the biological activity of essential cellular proteins.